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Yr 3 > Thyroid Hormone > Flashcards

Thyroid Hormone Flashcards

1
Q

_______is stored in the thyroid hormone

A

Iodine

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2
Q

What is another name for C cells

A

Parafollicular Cells

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3
Q

What do C cell secrete

A

Calcitonin (a peptide hormone

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4
Q

What can calcitonin cause

A

Medullary Carcinomas

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5
Q

what are thyroid epithelial cell s(thyrocytes) organised into

A

spherical follicles

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6
Q

What 3 hormones does the thyroid secrete?

A

T3, T4, and calcitonin

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7
Q

What is secreted more? T3 or T4

A

T4

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8
Q

what state is T3 in for it to be inactive

A

rT3

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9
Q

____ is more potent than T4

A

T3

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10
Q

How is T4 converted to T3

A

deiodinase enzyme (type 2)

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11
Q

where is the deiodinase found and how does it work

A

peripheral tissues - by cleaving iodine off the 5’ group

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12
Q

T3 binds with what and how

A

high affinity T3 receptors TRalpha and TRbeta

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13
Q

Which T makes the effect in the organ

A

T3

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14
Q

How many types of deiodinases are there

A

2 -> type 1 and type 2

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15
Q

Recite the affinity deiodinase for tissues in the blood

A

type 1 - low affinity
type 2 - high affinity

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16
Q

what else does type 2 deiodinase do?

A

provides T3 when free T4 falls to low levels (converts T4 to T3

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17
Q

where is thyroglobulin synthesized

A

thyroid epithelial cells

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18
Q

where is thyroglobulin secreted

A

lumen of the follicle

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19
Q

where is iodide taken up from

A

from the blood via sodium-iodide symporter
also transported into the colloid along with thyroglobulin

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20
Q

in what shape does the thyroid receptor function

A

heterodimer

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21
Q

TR-RXR binds to ______ on the target gene

A

thyroid response element (TRE)

22
Q

in absence of TH, TR-RXR does what

A

represses gene transcription through the recruitment of a corepressor complex containing histone deacetylase (HDAC)

23
Q

what are the two primary catergories of biological responses for thyroid hormones

A

Effects on cellular differentiation and development, on the nervous system in particular
Effects on metabolic pathways and use of carbohydrates, lipids and proteins

24
Q

T3 and T4 promote what

A

metabolism
increase oxygen consumption and heat production
help regulate basal metabolic rate and body temperature

25
Q

how does the thyroid hormone effect cardiovascular and respiratory effects

A

T3 increases oxygen use and cardiac output, ensuring sufficient oxygen delivery to the tissues. It alters cardiac function by altering the expression of many proteins e.g. increases the ryanodine Ca2+ channels in the sarcoplasmic reticulum, promoting Ca2+ release. It also enhances the sensitivity (and expression) of adrenoceptors (especially 1-receptors) to stimulation by noradrenaline

26
Q

How does the thyroid hormone effect basal metabolic rate

A

Thyroid hormones increase the basal rate of oxygen consumption and heat production (e.g., basal metabolic rate) moderated by a compensatory increase in heat loss through appropriate thyroid hormone-mediated increases in blood flow, sweating, and ventilation. Changes in body temperature parallel fluctuations in thyroid hormone availability. The overall metabolic effect has been described as accelerating the response to starvation.

27
Q

How does the thyroid hormone effect the ANS and catecholamine action

A

increasing the number of β-adrenergic receptors in heart muscle
increasing the generation of intracellular second messengers, such as cAMP

28
Q

how does the thyroid hormone affect the NS

A

enhances wakefulness, alertness, responsiveness to various stimuli

29
Q

When the hypothalamus releases TRH what does it stimulates and where

A

TSH in anterior pituitary

30
Q

glucocorticoids reduce what

A

the conversion of T4 to T3
decrease pituitary production of TSH

31
Q

What general affect does hyperthyroidism have on the body

A

increases everything

32
Q

What general affect does hypothyroidism have on the body

A

slows everything down

33
Q

give an example of hyperthyroidism and its origin

A

Graves disease -
autoantibodies stimulate thyrotropin receptors on thyroid follicle cells leading to continual stimulation of thyroid hormone synthesis

34
Q

what is secondary hyperthyroidism

A

excessive secretion of TSH from a TSH producing tumor

35
Q

Hypothyroidism can be caused by what

A

Hashimoto disease (huge neck)
antibodies attacking specific thyroid cellular components (thyroglobulin)
will not make efficient T3 or T4
dietary iodine deficiency

36
Q

what is goitre

A

enlarged thyroid gland - hypothyroidism
TSH secretion incraeses

37
Q

How is graves disease diagnosed

A

hyperthyroidism - elevated serum free and T4 / T3 levels

38
Q

what causes graves disease

A

serum TSH levels are too low because hypothalamus and the pituitary gland are inhibited by high levels of T4 and T3
——-»»> no TSH is being produced

39
Q

what drugs are used to treat hyperthyroidism

A

thioureylene (thionamide)
Iodine containing preparations
Beta - adrenoreceptor antagonists

40
Q

describe effects of thiuoreylenes, what causes patient to switch medication

A

CARBIMAZOLE or METHIMAZOLE often used first; common side effect is “skin rash”, so patient then switched to ..
PROPYLTHIOURACIL – additional useful action of inhibiting deiodinase enzyme that converts T4 to T3 in many tissues

41
Q

What is iodine containing preparations used in

A

hyperthyroidism

42
Q

what does iodine containing preparations produce and what happens because of this

A

Produces (gamma..) -rays and (mainly) beta-particles; short range of -particles causes localized cell damage to thyroid follicular cells – going to eliminate a portion of the thyroid gland

43
Q

what might happen when being treated with iodine containing preparations

A

cause hypothyroidism if too much gland damage
may need thyroid hormone replacement therapy

44
Q

who is iodine containing preparations not given to and why

A

pregnant mothers - could harm foetal thyroid

45
Q

what is another name for beta adreno receptor antagonists

A

propranolol

46
Q

how do beta adrenoreceptor antagonists work

A

used to block noradrenaline overstimulation of cardiac beta1 adrenoreceptors
Used to block noradrenaline overstimulation of cardiac 1-adrenoceptors
[Increased sympathetic nervous system (noradrenaline) activity in hyperthyroidism can cause dangerously increased heart rate (tachycardia) and abnormal heart rhythms (dysrhythmias)]

47
Q

what is used as replacement therapy for hypothyroidism and what is a side effect

A

synthetic T3 and T4
cardiac dysfunction if replacement therapy doese too high

48
Q

in the brain, where do T4 cells enter and what happens

A

glial cells, and is converted to T3

49
Q

how is T4 converted to T3

A

D2 deiodinase

50
Q

T3 exits the cell and does what

A

transported into a neuron via MCT8

51
Q

what happens in the neuron

A

enters the nucleus binding a TR, or is inactivated to T2 by D3 deiodianse

Yr 3 (15 decks)

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